Remove unused combination evidence and helpers

internal/engine/sequence_combine.go

@@ -23,7 +23,6 @@ type sequenceCombinationResult struct {
 	higherItems    []sequenceItemProjection
 	replacements   []sequenceItemReplacement
 	appendedHigher []int
-	discardedLower []int
 }
 
 func combineSequence(
@@ -36,7 +35,7 @@ func combineSequence(
 	}
 	switch policy.operation {
 	case sequenceModeReplace:
-		return replaceSequence(lower, higher, policy.effectiveIdentityFields, context)
+		return replaceSequence(higher, policy.effectiveIdentityFields, context)
 	case sequenceModeAppend, sequenceModeUpsert:
 		return combineIdentifiedSequences(lower, higher, policy.operation, policy.effectiveIdentityFields, context)
 	default:
@@ -55,7 +54,7 @@ func unchangedSequenceValue(lower *document.Node) sequenceCombinationResult {
 }
 
 func replaceSequence(
-	lower, higher *document.Node,
+	higher *document.Node,
 	identityFields []string,
 	context sequenceCombinationContext,
 ) (sequenceCombinationResult, []Diagnostic) {
@@ -68,9 +67,6 @@ func replaceSequence(
 	if higher.Kind == document.Sequence {
 		result.higherItems = sequenceItemProjections(len(higher.Sequence), 0)
 	}
-	if lower != nil && lower.Kind == document.Sequence {
-		result.discardedLower = sequenceIndexes(len(lower.Sequence))
-	}
 	return result, nil
 }